1. Field of the Invention
The invention relates to a picture display device, including a line synchronizing circuit implemented as a phase control loop for synchronizing a line oscillator with an incoming line synchronizing signal, and a line deflection circuit coupled to the oscillator for generating a line deflection current having a trace and a retrace through a line deflection coil, the coil being coupled to a correction device comprising modulation means for modulating the line deflection current.
2. Description of Related Art
Such a line deflection circuit is disclosed in European Patent Specification 13,598. This prior art circuit includes a modulator for field-frequency modulating the amplitude of the line deflection current for correcting the east-west distortion. A capacitor for the S-correction is arranged in series with the line deflection coil and the circuit is of such a construction that also the S-correction is subjected to a modulation at the field frequency. Also a linearity correction coil with a saturable core, which is included in the arrangement in such a manner, that also the magnitude of the linearity correction varies with field frequency, is arranged in series with the coil. The prior art circuit forms part of a color television receiver and the control signal thereof, coming from a line oscillator, has consequently the line frequency prescribed by a television standard.
The prior art circuit is, however, not suitable for use in a picture display device, for example a monitor in which the line frequency may have different values. Since the line oscillator is controlled, it is always capable of assuming the appropriate frequency, provided it is designed properly but it will be obvious that the line deflection current generated and corrected by means of a circuit comprising frequency-dependent elements cannot vary appropriately as a function of time for all the line frequencies applied.